Currently, there has been widely spread a photographic system in which a color photographic material for picture-taking (color negative film) is loaded into a camera, exposed, developed, and the developed color negative is printed on color print paper to obtain a color positive image (negative-positive system).
On the other hand, a reversal-type color photographic material for picture-taking (color reversal film), after exposed, is subjected only to reversal development to obtain a positive image, having advantages that the developed film is observed as it is or through a slide projector, or is printed to produce a positive color print (positive-positive system). However, the reversal photographic material is not as popular as the negative-positive system described above, because the photographic material is not suited for easy photographing because of narrow photographic latitude, and positive color prints are rather expensive.
Recently, there appeared in the market a prepackaged photographic unit, so-called lens-fitted film in which unexposed color negative film is packaged in the state ready for immediate exposure, leading to an increase of picture-taking opptunities to further promote the negative-positive system.
Along with the spread of the color photographic system, recently, black-and-white (or monochromatic) photographic camera material caused a small boom. This was contemplated to be due to the fact that black-and-white (or monochromatic) images are freshly appreciated and its unique portrayal is considered mysterious, compared to the common flooded color photographs.
The main users of conventional monochromatic photographic camera materials were primarily professionals and advanced amateurs. However, since "Torikkiri Konica Shirokuro" (Film-In-Mini Konica Black-and-White) was put on the market in April, 1995, everybody was allowed to enjoy basic photography using monochromatic photographic materials. As a result, the photographic industry could not help but direct its attention to be directed to this unexpectedly popular medium.
Silver image forming-type monochromatic photographic camera materials are entirely different in photographic processing from color photographic system of negative-positive process, producing problems such that troublesome selection and handling of monochromatic photographic materials was needed in the commercial processing facilities and a separate processing line for monochromatic photographic materials had to be installed.
There are known monochromatic photographic camera materials which are compatible with broadly popularized color photographic processing of the negative-positive system; for example, a monochromatic image forming photographic material by the use of a black coupler, as disclosed in U.S. Pat. Nos. 2,592,514 and 4,348,474; JP-B 63-59136 (herein, the term "JP-B" refers to examined and published Japanese Patent). U.S. Pat. Nos. 2,181,944, 2,186,736, 4,368,255 and 5,141,844; JP-A-57-56838, 57-5814758-215645, 3-107144, 6-214357 and 7-199421; and JP-A 6-505580 also disclose a technique of forming monochromatic dye image by using a mixture of yellow, magenta and cyan couplers.
Although processed in common with conventional processing, any of these had the problem that printing on print paper was troublesome. When the above-described technique is applied to conventional color development, either one of color forming components destroys, due to difference in reactivity of the couplers, the balance with other components. As a result, it becomes difficult to obtain neutral gray color in the overall density range or processing variation due to the concentration of a developing agent, pH, temperature or contamination (carrying-in of undesired material), making it difficult to stably form monochromatic images. Preferred as monochromatic prints in final image, are warm color tone, warm, nostalgic sepia color tone, therefore, easy making of these sepia-toned monochromatic prints is desired.
Further, even if monochromatic images can be formed in color negative development by combination with color print paper, and unless monochromatic paper printing suitability is provided, it is very difficult to respond to broad consumer needs.
In the case of forming monochromatic images with dyes, all of the couplers react in a high exposure region to cause nongranularity, leading to superior graininess in the high density region, as compared to a silver image. However, graininess in a low exposure region, on the contrary, is deteriorated, so that it is necessary to enhance graininess of monochromatic dye images in the low exposure region. Since the human eye is very sensitive to even slight color shift from neutral monotone, it is further necessary to design so as to produce a smooth tone, taking account of dependence of development and balance of developability with respect to high-sensitive, medium-sensitive and low-sensitive layers.